Objective To investigate the application of Onodera’s prognostic nutrition index (OPNI) and clinicalpathological features in risk evaluation of prognosis of gastric cancer patients. Methods The clinical data of 46 gastric cancer patients who underwent radical gastrectomy in our hospital during 2012 was analyzed retrospectively. The OPNI value was calculated by serum albiumin (g/L)+5×lymphocyte count (×109/L). The receiver operating characteristic (ROC) curve and Youden index were used to determine the cutoff value of the OPNI. Survival curves were describe by the Kaplan-Meier method and compared by the Log-rank test. The univariate and multivariate analyses were performed with Cox proportional hazard model to identify the prognostic factors. Results The mean values of the OPNI in negative lymph node, pTNM, normal CEA and CA199, no postoperative complication were significantly higher than those in patients without such factors. When the OPNI was 38.175, the Youden index was maximal. Tumor infiltration depth in high OPNI group was less than in low OPNI group. The proportion of lymph node invasion in high OPNI group was significantly lower than in low OPNI group. The overall survival rate in high OPNI group was higher than in low OPNI group. The univariate and multivariate analyses showed that patient age and OPNI were independent factors for predicting overall survival rate. Conclusions The OPNI value is a simple and intuitive tool to predict the prognosis of patients with gastric cancer.